Most of us use the clear plastic tubing. Do you mean you need it to rack from primary to the bottling bucket? Or to bottle the beer? If the later,you need a bottling wand,& they take a 3/8" tube. As do auto siphons. I have spigots on my primaries,& use a piece of tubing long enough to go from the spigot down to half way around the bottom of the bottling bucket.
For the bottling wand,i use the required 3/8" tubing in about 4 foot length. That way,I can sit down with everything needed to bottle within arm's reach.